Topic
Lift-induced drag
About: Lift-induced drag is a research topic. Over the lifetime, 2861 publications have been published within this topic receiving 41094 citations.
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TL;DR: In this paper, wind-tunnel tests were made from subsonic to hypersonic speeds to define the aerodynamic characteristics of the HL-20 lifting-body configuration, and the data have been assembled into an aerodynamic database for flight analysis of this proposed vehicle.
Abstract: Wind-tunnel tests were made from subsonic to hypersonic speeds to define the aerodynamic characteristics of the HL-20 lifting-body configuration. The data have been assembled into an aerodynamic database for flight analysis of this proposed vehicle. The wind-tunnel data indicated that the model was longitudinally and laterally stable (about a center-of-gravity location of 0.54 body length) over the test range from Mach 20 to 0.3. At hypersonic speeds, the HL-20 model trimmed at a lift/drag (L/D) ratio of 1.4. This value gives the vehicle a crossrange capability similar to that of the Space Shuttle. At subsonic speeds, the HL-20 has a trimmed LID ratio of about 3.6. Replacing the flat-plate outboard fins with fins haying an airfoil shape increased the maximum subsonic trimmed LID to 4.2.
46 citations
01 Jan 1923
TL;DR: In this paper, it was shown that the loss of lift in consequence of the mutual influence of the two wing sections is only half as much if the lift is produced by the curvature of the section as it is when the inclination of the chord to the direction of motion.
Abstract: This report deals with the air forces on biplane cellule. The first part of the report deals with the two-dimensional problem neglecting viscosity. The variation of the section, chord, gap, stagger, and decalage are investigated, a great number of examples are calculated, and all numerical results are given in tables. For the biplane without stagger it is found that the loss of lift in consequence of the mutual influence of the two wing sections is only half as much if the lift is produced by the curvature of the section as it is when the lift is produced by the inclination of the chord to the direction of motion. The second part deals with the influence of the lateral dimensions. It is found that the loss of lift due to induction is almost unchanged, whether the biplane is staggered or not. In the third part conclusions from previous investigations are drawn, viscosity and experimental experience are brought in, and the method is simplified for practical application. Simple formulas give the drag, lift, and moment. In order to make use of the simple formulas more convenient, tables for the dynamical pressure, induced drag, and angle of attack are added so that practically no computation is needed for the application of the results.
46 citations
Patent•
19 Dec 1977
TL;DR: In this paper, a wing extension or tip fin was disclosed wherein the tip fin is joined to an aircraft wing to form a nonplanar wing configuration which minimizes induced drag during both low speed and high speed operation of an aircraft.
Abstract: A wing extension or tip fin is disclosed wherein the tip fin is joined to an aircraft wing to form a nonplanar wing configuration which minimizes induced drag during both low speed and high speed operation of an aircraft. The tip fin which is of generally trapezoidal geometry, extends streamwise along the end of the aircraft wing and is canted to project upwardly and outwardly therefrom. Additionally, the tip fin is twisted to toe-out relative to the freestream direction with the angle of twist varying along the lower portion of the tip fin length. Viewed from the side, the tip fin has a sweep angle at least equal to the sweep angle of the aircraft wings with the leading edge of the tip fin intersecting the wing tip chord at a position aft of the wing leading edge. A strake which extends along the upper surface of the wing from the wing leading edge to the tip fin leading edge, forms a smooth transition between the wing and tip fin. To provide maximum aerodynamic efficiency, the length and cant angle of the tip fin are established to reduce the induced drag of the wing-tip fin combination below that exhibited by the wing alone or by a conventional wing of area and span equivalent to that of the combined wing-tip fin. Interference and compressibility drag of the combined wing-tip fin is minimized by controlling the chordwise position of the tip fin and by the strake which not only provides an aerodynamically smooth wing to tip fin transition, but establishes a vortical flow pattern that maintains boundary layer attachment under high speed flight conditions. Further, the area of the tip fin is established for minimum profile drag, the variation in tip fin thickness ratio further minimizing interference drag and the tip fin twist compensates for spanwise loading on the wing to reduce induced drag.
46 citations
28 Jun 2010
TL;DR: This research investigates methods for designing and optimizing winglet geometry for UAVs that operate at Reynolds numbers near 10 and applies the resulting methodology to existing UAV platforms for specific performance improvements.
Abstract: Winglets are known improve the efficiency of large aircraft at high subsonic speeds, but winglet designs for smaller aircraft such as UAVs are largely unproven. Winglets improve efficiency by diffusing the shed wingtip vortex, which in turn reduces the drag due to lift and improves the wing’s lift over drag ratio. This research investigates methods for designing and optimizing winglet geometry for UAVs that operate at Reynolds numbers near 10. The design methodology is based on the vortex lattice method. Optimized designs are tested and compared with base designs for validation and include both Whitcomb and blended winglets. Designs are validated using wind tunnel tests. The resulting methodology is then applied to existing UAV platforms for specific performance improvements.
46 citations
TL;DR: In this article, a span morphing concept, the Gear driveN Autonomous Twin Spar (GNATSpar) for a mini-UAV, is proposed to achieve span extensions up to 20% to reduce induced drag and increase flight endurance.
46 citations